1. Field of the Invention
The present invention relates to a fixing apparatus used in developing an image.
2. Description of Related Art
In general, a fixing apparatus is used in an image forming apparatus such as electro-photographic printer, copy machine etc. Such a fixing apparatus comprises; at least a heating roller containing heater, a pressuring roller pressed to the heating roller and rotated by the heating roller, a fixing belt put on the heating roller etc. Then, said heating roller, pressuring roller and fixing belt comprise a fixing nip. And, print media holding unset toner image, is passed through this fixing nip. Thereby, the toner image is fixed to the print media. This is a fixing apparatus using a method of heating roller.
FIG. 2 is a side view showing configuration of a conventional fixing apparatus.
In FIG. 2, 111 indicates a first heating roller. 112 indicates a fixing belt, 113 indicates a second heating roller, and 114 indicates a pressuring roller. Here, said first heating roller 111 and second heating roller 113 are respectively provided with halogen lamps as internal heating means. Thereby, said fixing belt is heated. Moreover, said pressuring roller 114 is placed confronting with said second heating roller 113. And, it is pressed to the second heating roller 113 with the fixing belt therebetween. Thereby, they comprise a fixing nip. And, print media 115 holding unset toner image, passes through the fixing nip comprising said second heating roller 113, fixing belt 112 and pressuring roller 114. Thereby, the toner image is fixed to the print media 115.
In above conventional fixing apparatus, a temperature detecting sensor not shown in the drawings is provided at a central portion of the fixing belt 112 in direction of its width. Thereby, temperature control is performed in order to settle temperature of said fixing belt 112 to a fixed value. However, when print media 115 with narrow width continuously pass through the fixing nip; both end portions in direction of width of fixing belt 112, temperature rises; because print media 115 do not pass at both end portions of fixing belt 112, where heat is not taken away by print media 115. Therefore, there can be case that inconvenience such as offset caused by hot end portions, gross blotches etc. occurs.
Accordingly, in order to cope with temperature rise in the fixing belt 112, cooling devices such as cooling fans, Peltier elements, etc. are used. The fixing belt 112 is therefore cooled when the temperature of fixing belt 112 rises. This kind of fixing apparatus is disclosed in, for example, JP 2001-42672.
However, in said conventional fixing apparatus, heat in the fixing belt is taken away by radiating it in the air. Therefore, availability of heat energy in the fixing apparatus decreases.